Nitrous Oxide Safety for Hybrid Rockets
- Paper number
IAC-12,C4,2,14.p1,x12935
- Author
Mr. Benjamin Waxman, Stanford University, United States
- Author
Mr. Jonah Zimmerman, Stanford University, United States
- Coauthor
Prof. Brian Cantwell, Stanford University, United States
- Year
2012
- Abstract
In recent years, nitrous oxide has gained popularity as a propellant for hybrid rocket systems due to its ease of handling, storability, and self-pressurization characteristics. Since nitrous oxide is widely used in automobile racing, anesthesia, and the food industry, it is commonly treated as a safe, non-hazardous material. However, exothermic decomposition reactions are possible with nitrous oxide, and have resulted in multiple catastrophic failures, even causing loss of life. In this paper several such incidents involving hybrid rockets are examined, detailing their causes and consequences. In order to develop guidelines for the safe design and operation of hybrid rockets utilizing nitrous oxide, it is important to first have an understanding of the underlying thermochemical and kinetic mechanisms. Typically with pure nitrous oxide, the activation energy is sufficiently high to prevent thermal decomposition reactions under a wide range of operating conditions. However, contamination with even minute levels of hydrocarbons has been shown to drastically reduce this activation energy, increasing the potential for explosion. Dilution of the vapor with gases such as oxygen or helium has been shown to mitigate this hazard. As a result of theoretical analysis and experimental data, simple guidelines have been developed to reduce the likelihood of explosive decomposition when using nitrous oxide in hybrid rocket propulsion systems. Some of these guidelines are listed below: \begin{itemize} \item Use standard oxygen system cleaning procedures on all components contacting nitrous oxide \item Strictly obey material compatibility rules \item Shut down the motor before the liquid is completely consumed \item Minimize flow disturbances in the propellant feed lines \item Eliminate spaces within the motor where gaseous nitrous oxide may accumulate \item Treat nitrous oxide as a hazardous material \item Maintain safe distance for all personnel when running motors, performing cold flow tests, or pumping and transferring nitrous oxide \item Prevent heating of nitrous oxide vapor \item Provide sufficient ullage for liquid expansion due to warming \end{itemize} When these rules are followed, hybrid rockets utilizing nitrous oxide can be simple, safe, and high-performance. However, as with all energetic materials it should be treated with the utmost respect.- Abstract document
- Manuscript document
(absent)